ABSTRACT

Although Bt insecticides remain effective, LC₅₀ values recorded for bollworm larvae, collected and evaluated in 2003, were approximately 2-3 times higher than previously recorded during 1996 through 1997. Bollworm populations have remained susceptible to pyrethroid insecticides; however, tobacco budworm larvae are 10-25 times more resistant to cypermethrin when compared to the most susceptible field strain and laboratory susceptible strains. Furthermore, LC₉₅ values gave increased sharply during the nine year study period. Spinosad remains the most effective insecticide tested to date.